Method for producing a composite layer

ABSTRACT

Disclosed is a method for forming a composite layer, in which a mixture of the inorganic particles and the thermoplastic resin are flame sprayed to a substrate at a temperature of not less than the glass transition point of the thermoplastic resin and not more than melting point of the inorganic particles, wherein the mixture comprises 85-99% by weight of the inorganic particles and 15-1% by weight of the thermoplastic resin, total weight of the mixture being 100% by weight.

FIELD OF THE INVENTION

The present invention relates to a producing method of a composite layerby flame spraying a mixture of inorganic substance and an organicsubstance, and a composite panel which can be utilized for a radiationimage conversion panel by using a phosphor as the inorganic substance.

RELATED ART

A flame spraying method is widely applied for treating the surface ofvarious members. The substrate to be flame sprayed includes manymaterials such as wood, ceramics, cement and metal. The object and useof the treatment is expanded to giving abrasion-resistant ability,anti-corrosion ability and heat insulating ability, surface propertyimproving and thickening.

Various composite layers can easily formed by the flame spraying method,for example, a composite layer of ceramics and metal and that of resinand inorganic element have been known. For example, a particle of amixture of nylon and epoxy resin for flame spraying is proposed, cf.Patent Document 1. A method for forming an ablatable layer by flamespraying particles composed of aluminum and polyester resin isdisclosed, cf. Patent Document 2. Moreover, a method is concretelydisclosed, in which flame spraying is performed at a low temperature sothat the resin particles are only melted and the inorganic resinparticles are not melted, cf. Patent Document 3.

The methods described in the above patent documents are proposed forproducing the layers superior in the anti-corrosion and ant-abrasionabilities. However, the layers have a high content of resin and a lowcontent of inorganic element. Consequently, sufficient properties cannotbe obtained some times for a specific use. In concrete, in a compositelayer utilizing the optical property of an inorganic particle, light iseasily scattered in the layer when the resin content in the layer ishigh since the difference of refraction index of the resin and that ofthe inorganic material is usually large. Moreover, the resin itselfabsorbs the light in some cases so that the property of the inorganicparticle is difficultly displayed.

On the other hand, a method for directly outputting an image from aphosphor layer composed of inorganic particles by employing a compositelayer utilizing the optical property of the inorganic particle. In suchthe method, radiation permeated trough an object is absorbed by astimulable phosphor and then the radiation energy absorbed andaccumulated by the phosphor is emitted by stimulating by light orthermal energy and the emitted light is detected for imaging.

In concrete, for example, the radiation image conversion methodsemploying the phosphors described in U.S. Pat. No. 3,859,527 and JP-ANo. 55-12144 have been known.

In this method, a radiation image conversion panel is employed;radiation permeated through an object is irradiated to the phosphorlayer of the radiation image conversion panel so that the radiationenergy corresponding to the permeation density of each part of theobject is accumulated in the phosphor layer, and then the radiationenergy is emitted as stimulating light emission by time seriallystimulating the phosphor layer by electromagnetic wave such as visiblerays or infrared rays. Thus obtained signals according to the intensityvariation of the emitted light is converted to, for example, electricalsignals by photo-electro conversion, and the signals are reproduced as avisible image on a recording material such as a silver halidephotographic material or a CRT.

Such the reproduction method of radiation method has an advantage that aradiation image rich in information amount can be obtained byconsiderably small amount of exposing radiation compared with thatnecessary for the combination of a photographic material for radiationrecording and an intensifying screen.

The phosphor is a phosphor capable of emitting stimulation emissionlight by irradiation by the stimulation light after irradiation by theradiation; a phosphor emitting light having a wavelength of 300 to 500nm by the stimulating light having a wavelength of 400 to 900 nm isusually employed in the practical use.

The radiation image conversion panel employing such the phosphorreleases the accumulated energy by the scanning by the stimulatinglight, therefore, the panel can accumulate again a radiation image afterthe scanning so as to be used repeatedly. Namely, the radiation imageconversion method is also advantageous from the viewpoint of resourcessaving and economical efficiency since the radiation image conversionpanel is repeatedly used in this method compared with the usualradiation photographic method in which the radiation photographic filmis consumed for every one image taking.

It is preferable that the stimulation light for scanning is difficultlyscattered in the phosphor layer. For making such the situation, it isrequired to raise the density of the phosphor and to reduce the distancebetween the particles. When the phosphor particles are layered togetherwith a large amount of a binder, the distances between the particles areenlarged and the degradation of the sharpness caused by the lightscattering cannot be avoided.

As countermeasures to the above problems, a method for forming a layerhaving phosphor light emitting function by plasma spraying phosphorpowder onto a substrate surface, cf. Patent Document 4, and a method forforming the stimulable phosphor layer by a flame spraying method and agas phase sedimentation method, cf. Patent Document 5, are proposed.However, the shape and the particle diameter distribution of thephosphor formed on the substrate are difficultly controlled and thesharpness is difficultly raised since the phosphor is supplied in themelted state in the both methods.

-   -   Patent Document 1: JP-A No. 58-13666    -   Patent Document 2: JP-A No. 1-128144    -   Patent Document 3: JP-A No. 9-314032    -   Patent Document 4: JP-A No. 63-169370    -   Patent Document 5: JP-A No. 1-131500

SUMMARY OF THE INVENTION

An object of the invention is to provide a method for forming a uniformcomposite layer containing inorganic particles holing the propertiesthereof and a particle including the inorganic particle to be used inthe method, which can flame sprayed, and to provide the composite layercontaining a phosphor having high luminance and sharpness by using thephosphor as the inorganic material and a radiation image conversionpanel using the composite layer.

From one aspect, a composite layer comprising inorganic particles and athermoplastic resin is formed by this invention, the method comprises astep of

-   -   flame spraying a mixture or the inorganic particles and the        thermoplastic resin particles to a substrate, wherein each of        the inorganic particles and the thermoplastic resin particles        has a temperature of not less than the glass transition point of        the thermoplastic resin and not more than the melting point of        the inorganic particles, and    -   the mixture comprises from 85 to 99% by weight of the inorganic        particles and from 15 to 1% by weight of thermoplastic resin        particles, total weight of the mixture being 100% by weight.

The other aspect is a method for forming a composite layer comprisinginorganic particles and a thermoplastic resin by flame sprayingcomposite particles each of particles comprises the inorganic particlesand a thermoplastic resin.

A method for forming a uniform composite layer containing inorganicparticles without degradation of propertied thereof and a thermoplasticresin can be provided by the invention. A radiation image conversionphosphor layer having high sharpness and high luminance and a radiationimage conversion panel employing the layer can be provided by employinga phosphor as the inorganic particles.

The invention is described in detail below.

The inventors have investigated the method for producing the compositelayer containing the inorganic particles and the thermoplastic resin.The composite layer is formed by spraying the mixture having a contentof the inorganic particles of from 85% to 99% by weight and a content ofthe thermoplastic particles of from 1.0% to 15% by weight whilecontrolling the temperature of a mixture of the inorganic particles andthe thermoplastic particles so that the temperature is not less than theTg of the thermoplastic resin at which the thermoplastic resin is meltedor partially melted and not more than the melting point of the inorganicparticle at which the inorganic particle is not melted or not partiallymelted. The thermoplastic resin is preferably contained in the mixturein a state of particles.

From another viewpoint, the composite layer can be formed by flamespraying composite particles each comprising the thermoplastic resin andthe inorganic particles. It is preferable that the inorganic particlesare previously subjected to a surface treatment by a silane couplingagent.

The high luminance and the sharpness can be attained by the compositelayer forming method according to the invention since the inorganicparticles are sprayed at a temperature at which the inorganic particlesare not melted or not partially molted while holding the shape and thedistribution together with extremely small amount of the thermoplasticresin so as to form the layer uniformly having the properties, becausethe inorganic particles prepared by exactly controlling are notsubjected to a re-melting process which is applied in the plasmaspraying method and the gas sedimentation method such as PVD and CVD.

Hereinafter, the method by flame spraying the mixture is referred to as“a mixture flame spraying method”. The mixture employed in the mixtureflame spraying method has a content of inorganic particles of from 85%to 99% by weight and a content of the thermoplastic resin particle offrom 1.0 to 15% by weight, the total mount of the mixture being 100% byweight. The composite layer can be formed by such the composition, whichhas the sufficient strength and uniformly contains the inorganicparticles in high density so that the spreading of scattered light issmall.

Various kinds of thermoplastic resin can be employed. For example, apolyethylene resin, polypropylene resin, nylon-11 resin, nylon 12 resin,ethylene-vinyl acetate copolymer resin, ethylene-acrylic acid copolymerresin, ethylene-methacrylic acid copolymer resin, modified polyethyleneresin and modified polypropylene resin are employable. These resins maybe used in an optional combination.

The diameter of the thermoplastic resin particle to be used for theflame spraying is from 0.1 to 500 μm and more preferably from 1 to 100μm. The diameter and the amount of the thermoplastic resin particles areselected according to the using object of the composite layerconsidering the amount and the particle diameter of the inorganicmaterial.

From another viewpoint, the method of the invention is a method forforming the composite layer by flame spraying composite particlescomposed of the thermoplastic resin and the inorganic particles.

The inorganic particles are different from the thermoplastic resin inthe specific gravity and the surface area; therefore, the spraying ratesof them are different from each other so that the formation of thecomposite layer uniformly comprising the inorganic articles and thethermoplastic resin is difficult a little when the mixture of them issprayed in untouched state.

The unevenness of the layer composition caused by the difference of thespraying rate can be inhibited by flame spraying the composite particlescontaining the previously prepared inorganic particles and thethermoplastic resin. Such the method is advantageous since the method iseasily controlled for giving a slant in the content of the inorganicparticles in the layer composition. In the usual flame spraying, thediameter of the inorganic particle is necessary to be severalmicrometers or more; the particle diameter can be made larger by formingthe composite particle containing plural particles when the particlediameter is submicron class. Consequently, the flame spraying can bestably performed without any variation in the diameter of primaryparticles.

Namely, the inorganic particle having a diameter of submicron class canbe contained in the composite layer without any variation in thediameter by flame spraying under a condition in which the thermoplasticis only melted and the inorganic particles is not melted so that thenecessary properties of the inorganic particle can be maintained. Whenthe inorganic particles melted at high temperature are sprayed, theinorganic particles are combined with other particles or the chemical orphysical property of the surface is varied, accordingly the propertiesof the original particles are difficultly maintained.

The composing state of the inorganic particles and the thermoplastic cantake various forms such as one having a core/shell structure in whichthe core of the inorganic particle included by the shell of thethermoplastic resin, one having a reverse structure of the above and onehaving a plural dimensional state in which plural composite particlesadhering with each other. Among them, the core/shell particle ispreferable, in which a part (preferably not less than 50%, and more notless than 80%, in area ratio) or the entire surface of the inorganicparticle is covered with the thermoplastic resin. The ratio of theinorganic particles is preferably from 85 to 99% by weight of thecore/shell type particle.

Examples of the preparation method of the composite particle composed ofthe thermoplastic resin and the inorganic particles according to theinvention are described below.

Various methods such as those described below can be optionally selectedaccording to the situation of the flame spraying:

-   -   (1) A method in which a monomer as the raw material of the        thermoplastic resin is dropped into a suspension of the        inorganic particles for performing interface polymerization.    -   (2) A method in which the inorganic particles are dispersed in a        solution of the thermoplastic resin and then the solubility of        the resin is lowered or the solvent of the thermoplastic resin        is evaporated so as to be deposited the thermoplastic resin on        the surface of the inorganic particles.    -   (3) A method in which the inorganic particles are deposited on        the thermoplastic resin particles by a sol-gel method.

For the thermoplastic resin for preparing the composite particle, thethermoplastic resin usable for the flame spraying can be employed.

The inorganic particles are preferably treated by a silane couplingagent before the flame spraying or the preparation of the compositeparticles.

The treatment of the inorganic particle surface by the silane couplingagent is effective to raise the affinity of the inorganic particle withthe thermoplastic resin so as to form the composite layer higher in thestrength. Sufficient strength of the composite layer can be obtainedeven when the content of the thermoplastic resin is extremely lowered toa content of from 1.0 to 1.5% by weight.

Silane coupling agents usable in this invention are not specificallylimited but compounds represented by the following formula (1) arepreferred:

wherein R is an aliphatic or aromatic hydrocarbon group, which may beintervened with an unsaturated group (e.g., vinyl) or may be substitutedby R₂OR₃—, R₂COOR₃—, R₂NHR₃— (in which R₂ is an alkyl group or an arylgroup, and R₃ is an alkylene group or an arylene group) or othersubstituents; X₁, X₂ and X₃ are each an aliphatic or aromatichydrocarbon group, acyl group, amido group, alkoxy group,alkylcarbonyloxy group, epoxy group, mercapto group or a halogen atom,provided that at least one of X₁, X₂ and X₃ is a group other than thehydrocarbon group. X₁, X₂ and X₃ are preferably a group subject tohydrolysis.

Specific examples of the silane coupling agent of formula (I) includemethyltrimethoxysilane, methyltriethoxysilane, vinyltriacetoxysilane,vinyltrichlorosilane, vinyltriethoxysilane,γ-chloropropyltrimethoxysilane, γ-chloropropylmethyldichlorosilane,γ-chloropropyl-methyldimethoxysilane,γ-chloropropylmethyldiethoxysilane, γ-aminopropyltriethoxysilane,N-(β-aminoethyl)-γ-aminopropyl-trimethoxysilane,N-(β-aminoethyl)-γ-aminopropylmethyl-dimethoxysilane,γ-mercaptopropyltrimethoxysilane, γ-mercaptopropylmethyldimethoxysilane,γ-glycidoxypropyl-trimethoxysilane,γ-methacryloxypropyltrimethoxysilane,γ-methacryloxypropylmethyldimethoxysilane,γ-(2-amonoethyl)-aminopropyltrimethoxysilane,γ-isocyanatepropyltriethoxy-silane,γ-(2-aminoethyl)aminopropylmethyldimethoxysilane,γ-anilinopropyltrimethoxysilane, vinyltrimethoxysilane, andN-β-(N-vinylbenzylaminoethyl)-γ-aminopropyltrimethoxy-silane.hydrochloricacid salt or aminoslane composite. Of these, vinyl type, mercapto type,glycidoxy type and methacryloxy type are preferred. In the embodimentsof this invention, the silane coupling agent preferably contains amercapto group, such as γ-mercaptopropyltrimethoxysilane andγ-mercaptopropylmethyldimethoxysilane.

The methods for providing the treatment onto the surface of theinorganic particles include a dry method in which the silane couplingagent is dropped or sprayed to the inorganic particles while stirring tomix the particles, a slurry method in which the silane coupling agent isdropped into the phosphor in a slurry state while stirring and then theinorganic particles are precipitated, filtered and dried to remove theremaining solvent, and a method in which the inorganic particles aredispersed in a solvent and the silane coupling agent is added to thedispersion and stirred and then the solvent is evaporated to form aadhering layer on the surface of the inorganic particles.

It is preferable for making certain the reaction between the silanecoupling agent and the inorganic particles that the inorganic particlestreated by the silane coupling agent are dried for a time of from 10 to200 minutes at a temperature of from 60 to 130° C. Example of the methodsuch the treatment is a method in which the inorganic particles areloosened in a dispersion of the inorganic particles and the silanecoupling agent so that the covering by the hydrophilic fine particlesand the surface treating by the silane coupling agent are simultaneouslyperformed with the loosen of the inorganic particles and the inorganicparticles are filtered and dried.

The inorganic particle is described below.

In the invention, an organic particle such as powder of an oxide, ahydroxide, a carbonate, a sulfate, a silicate, a nitride, carbon, ametal and a ceramics are preferably employable.

Examples of the oxide include silica, diatomite, alumina, zinc oxide,titanium oxide, calcium oxide, magnesium oxide, iron oxide, tin oxide,antimony oxide and ferrite. Examples of the hydroxide include calciumhydroxide, magnesium hydroxide, aluminum hydroxide and basic magnesiumhydroxide. Examples of the carbonate include calcium carbonate,magnesium carbonate, zinc carbonate, dawsonite and hydrotalcite.

Examples of the sulfate include calcium sulfate, aluminum sulfate,barium sulfate and lithopone. Examples of the silicate include calciumsilicate such as worastnite and xonotlite, aluminum silicate such asclay, talk, mica, mommolinite, silica sand, kaolin, powder of pumice,zeolite, bentonite, activated clay, slate powder, sepiorite, imogorite,serisite, glass fiber, gas beads, glass flake and silica balloon.

Examples of the nitride include aluminum nitride, boron nitride andsilica nitride.

Examples of the carbon include carbon black, graphite, carbon fiber,activated carbon, activated carbon fiber, fullerene, carbon nanotube,carbon balloon, and charcoal powder. Other than the above-mentioned,calcium titanate, aluminum borate, titanium zirconium, molybdenumsulfide, silicon carbide and zinc borate can be cited.

The diameter of the inorganic particle can be optionally selectedaccording to the use. A sphere-equivalent diameter of from 0.1 to 500 μmis preferred. The shape of the particle such as spherical, planar andneedle-like can be also selected according to the use.

It is preferable to use various phosphors as the inorganic particlehaving the optical property.

Examples of the stimulable phosphor used in the radiation imageconversion panel include,

-   -   (1) a rare earth activated alkaline earth metal fluorohalide        phosphor represented by the formula of (Ba_(1-x),M²⁺x)FX:yA, as        described in JP-A No. 55-12145, in which M²⁺ is at least one of        Mg, Ca, Sr, Zn and Cd; X is at least one of Cl, Br and I; A is        at least one of Eu, Tb, Ce, Tm, Dy, Pr, Ho, Nd, Yb, and Er; x        and y are numbers meeting the conditions of 0≦x≦0.6 and 0≦y≦0.2;        and the phosphor may contain the following additives:

-   a) X′, BeX″ and M³X₃′″, as described in JP-A No. 56-7417.5 (in which    X′, X″ and X′″ are respectively at least a halogen atom selected    from the group of Cl, Br and I; and M³ is a trivalent metal);

-   b) a metal oxide described in JP-A No. 55-160078, such as BeO, BgO,    CaO, SrO, BaO, ZnO, Al₂O₃, Y₂O₃, La₂O₃, In₂O₃, SiO₂, TiO₂, ZrO₂,    GeO₂, SnO₂, Nb₂O₅ or ThO₂;

-   c) Zr and Sc described in JP-A No. 56-116777;

-   d) B described in JP-A No. 57-23673;

-   e) As and Si described in JP-A No. 57-23675;

-   f) M.L (in which M is an alkali metal selected from the group of Li,    Na, K, Rb and Cs; L is a trivalent metal Sc, Y, La, Ce, Pr, Nd, Pm,    Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Al, Ga, In, and Tl) described in    JP-A 58-206678;

-   g) calcined tetrafluoroboric acid compound described in JP-A No.    59-27980;

-   calcined, univalent or divalent metal salt of hexafluorosilic acid,    hexafluorotitanic acid or hexafluorozirconic acid described in JP-A    No. 59-27289;

-   NaX′ described in JP-A No. 59-56479 (in which X′ is at least one of    Cl, Br and I);

-   h) a transition metal such as V, Cr, Mn, Fe, Co or Ni, as described    in JP-A No. 59-56479;

-   M¹X′, M′²X″, M³X′″ and A, as described in JP-A No. 59-75200 (in    which M¹ is an alkali metal selected from the group of Li, Na, K, Rb    and Cs; M′² is a divalent metal selected from the group of Be and    Mg; M³ is a trivalent metal selected from the group Al, Ga, In and    Tl; A is a metal oxide; X′, X″ and X′″ are respectively a halogen    atom selected from the group of F, Cl, Br and I);

-   i) M¹X′ described in JP-A No. 60-101173 (in which M¹ is an alkali    metal selected from the group of Rb and Cs; and X′ is a halogen atom    selected from the group of F, Cl, Br and I);

-   j) M²′X′₂.M²′X″₂ (in which M²′ is at least an alkaline earth metal    selected from the group Ba, Sr and Ca; X′ and X″ are respectively a    halogen atom selected from the group of Cl, Br and I, and X′ is not    X″); and    -   LnX″₃ described in JP-A No. 61-264084 (in which Ln is a rare        earth selected from the group of Sc, Y, La, Ce, Pr, Nd, Pm, Sm,        Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu; X″ is a halogen atom selected        from the group of F, Cl, Br and I);    -   (2) a divalent europium activated alkaline earth metal halide        phosphor described in JP-A No. 60-84381, represented by the        formula of M²X₂.aM²′₂:xEu²⁺ (in which M² is an alkaline earth        metal selected from the group of Ba, Sr and Ca; X and X′ is a        halogen atom selected from the group of Cl, Br and I and X≠X′; a        and x are respectively numbers meeting the requirements of        0≦a≦0.1 and 0≦x≦0.2);    -   the phosphor may contain the following additives;

-   a) M¹X″ described in JP-A No. 60-166379 (in which M¹ is an alkali    metal selected from the group of Rb, and Cs; X″ is a halogen atom    selected from the group of F, Cl, Br and I;

-   b) KX″, MgX₂′″ and M³X₃″″ described in JP-A No. 221483 (in which M³    is a trivalent metal selected from the group of Sc, Y, La, Gd and    Lu; X″, X′″ and X″″ are respectively a halogen atom selected from    the group of F, Cl Br and I;

-   c) B described in JP-A No. 60-228592;    -   an oxide such as SiO₂ or P₂O₅ described in JP-A No. 60-228593;    -   LiX″ and NaX″ (in which X″ is a halogen atom selected from the        group of F, Cl, Br and I;

-   d) SiO₂ described in JP-A No. 61-120883;    -   SnX₂″ described in JP-A 61-120885 (in which X″ is a halogen atom        selected from the group of F, Cl, Br and I;

-   e) CsX″ and SnX₂′″ described in JP-A No. 61-235486 (in which X″ and    X′″ are respectively a halogen atom selected from the group of F,    Cl, Br and I;    -   CsX″ and Ln³⁺ described in JP-A 61-235487 (in which X″ is a        halogen atom selected from the group of F, Cl, Br and I; Ln is a        rare earth element selected from the group of Sc, Y, Ce, Pr, Nd,        Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu;    -   (3) a rare earth element activated rare earth oxyhalide phosphor        represented by the formula of LnOX:xA, as described in JP-A No.        55-12144 (in which Ln is at least one of La, Y, Gd and Lu; A is        at least one of Ce and Tb; and x is a number meeting the        following condition, 0<x<0.1);    -   (4) a cerium activated trivalent metal oxyhalide phosphor        represented by the formula of M(II)OX:xCe, as described in JP-A        No. 58-69281 (in which M(II) is an oxidized metal selected from        the group of Pr, Nd, Pm, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb and Bi;        X is a halogen atom selected from the group of Cl, Br and I; x        is a number meeting the following condition, 0<x<0.1;    -   (5) a bismuth activated alkali metal halide phosphor represented        by the formula of M(I)X:xBi, as described in JP-A No. 62-25189        (in which M(I) is an alkali metal selected from the group of Rb        and Cs; X is a halogen atom selected from the group of Cl, Br        and I; x is a number meeting the following condition, 0<x≦0.2;    -   (6) a divalent europium activated alkaline earth metal        halophosphate phosphor represented by the formula of        M(II)₅(PO₄)₃X:xEu²⁺, as described in JP-A No. 60-141783 (in        which M(II) is an alkaline earth metal selected from the group        of Ca, Sr and Ba; X is a halogen atom selected from the group of        F, Cl, Br and I; x is a number meeting the following condition,        0<x≦0.2);    -   (7) a divalent europium activated alkaline earth metal        haloborate phosphor represented by the formula of        M(II)₂BO₃X:xEu², as described in JP-A No. 60 157099 (in which        M(II) is an alkaline earth metal selected from the group of Ca,        Sr and Ba; X is a halogen atom selected from the group of Cl, Br        and I; x is a number meeting the following condition, 0<x≦0.2);    -   (8) a divalent europium activated alkaline earth metal        halophosphate phosphor represented by the formula of        M(II)₂PO₄X:xEu²⁺, as described in JP-A No. 60-157100 (in which        M(II) is an alkaline earth metal selected from the group of Ca,        Sr and Ba; X is a halogen atom selected from the group of Cl, Br        and I; x is a number meeting the following condition, 0<x≦0.2);    -   (9) a divalent europium activated alkaline earth metal        hydrogenated halide phosphor represented by the formula of        M(II)HX:xEu²⁺, as described in JP-A No. 60-217354 (in which        M(II) is an alkaline earth metal selected from the group of Ca,        Sr and Ba; X is a halogen atom selected from the group of Cl, Br        and I; x is a number meeting the following condition, 0<x≦0.2);    -   (10) a cerium activated rare earth complex halide phosphor        represented by the formula of LnX₃.aLn′X₃′:xCe³⁺, as described        in JP-A No. 61-21173 (in which Ln and Ln′ are individually a        rare earth element selected from the group of Y, La, Gd and Lu;        X and X′ are respectively a halogen atom selected from the group        of F, Cl, Br and I and X+X′; a and x are respectively        numbers-meeting the following conditions, 0.1<a≦10.0 and        0<x≦0.2;    -   (11) a cerium activated rare earth complex halide phosphor        represented by the formula of LnX₃.aM(I)X′:xCe³⁺, as described        in JP-A 61-21182 (in which Ln and Ln′ are respectively a rare        earth element selected from the group of Y, La, Gd and Lu; M(I)        is an alkali metal selected from the group of Li, Na, k, Cs and        Rb; X and X′ are respectively a halogen atom selected from the        group of Cl, Br and I; a and x are respectively numbers meeting        the following conditions, 0.1<a≦10.0 and 0<x≦0.2;    -   (12) a cerium activated rare earth halophosphate phosphor        represented by the formula of LnPO₄.aLnX₃:xCe³⁺, as described in        JP-A No. 61-40390 (in which Ln is a rare earth element selected        from the group of Y, La, Gd and Lu; X is a halogen atom selected        from the group of F, Cl, Br and I; a and x are respectively        numbers meeting the following conditions, 00.1<a≦10.0 and        0<x≦0.2;    -   (13) a divalent europium activated cesium rubidium halide        phosphor represented by the formula of CsX:aRbX′:xEu²⁺, as        described in JP-A No. 61-236888 (in which X and X′ are        individually a halogen atom selected from the group of Cl, Br        and I; a and x are respectively numbers meeting the following        conditions, 0.1<a≦10.0 and 0<x≦0.2;    -   (14) a divalent europium activated complex halide phosphor        represented by the formula of M(II)X₂.aM(I)X′:xEu²⁺, as        described in JP-A No. 61-236890 (in which M(II) is an alkaline        earth metal selected from the group of Ba, Sr and Ca; M(I) is an        alkali metal selected from the group of Li, Rb and Cs; X and X′        are respectively a halogen atom selected from the group of Cl,        Br and I; a and x are respectively numbers meeting the following        conditions, 0.1<a≦20.0 and 0<x≦0.2.

Among the above-mentioned stimulable phosphors, stimulable phosphorparticles each containing iodine are preferable. A di-valenteuropium-activated alkali-earth metal fluoride halide typeiodine-containing phosphor, a di-valent europium-activated alkali-earthmetal halide type iodine-containing phosphor, a rare earthelement-activated rare element oxohalide type iodine-containing phosphorand a bismuth-activated alkali halide type iodine-containing phosphorare preferable since they emit stimulation light with high luminance,and an Eu-added BaFI compound is preferred as the stimulable phosphor.The particle size of the stimulable phosphor is preferably from 1 to 50μm.

In the production method of the composite layer, the layer is formed byflame spraying the mixture of the inorganic particles and thethermoplastic resin particles or the composite particles whilecontrolling the temperature at a level at which the thermoplastic resinis melted or partially melted and the inorganic particle is notpartially or entirely melted. Practically, a temperature not less thanthe glass transition point of the thermal resin and not more than themelting point of the inorganic particle.

Though various methods such as a plasma spraying method, a pressurereducing flame spraying method, a high velocity flame spraying method(HVOF), an electric arc spraying method and a gas flame spraying methodare applicable for the production method of the composite layer, and thegas flame spraying method is preferred since by which spraying at a lowtemperature can be easily performed for preventing the oxidation orburning of the thermoplastic resin used in the spraying.

In the gas flame spraying method, the materials are sprayed by gas flamewhich is controlled at a flame temperature of from 200 to 1200° C. and aflame velocity of from 80 to 200 m/second using, for example, propanegas, propylene gas, butane gas, hydrogen gas or kerosene as the mainburning gas and oxygen or air as the burning aid. It is preferable thatthe surface of the substrate to be sprayed is roughen to a center linesurface roughness of from 1 to 15 μm and previously heated at atemperature of from 70 to 250° C., and then the spraying is performed.

As the substrate, for example, various kinds of polymer material, glassand metal are employed. The shape of the substrate may be planar,complexly irregular or curved.

On thus formed composite layer, a protective film may be provided. Forthe protective film, for example, a polyester film, polymethacrylatefilm, nitrocellulose film and cellulose acetate film are employable, andan elongated film of poly(ethylene terephthalate) or poly(ethylenenaphthalate) is preferred for the protective layer from the viewpoint ofthe transparency and the strength. Moreover, the poly(ethyleneterephthalate) film or the poly(ethylene naphthalate film) on which athin layer of a metal oxide or silicon nitride is vapor deposited isalso preferred.

The thickness of said stimulable phosphor layer varies depending on thetarget characteristics of the radiation image conversion panel, thetypes of stimulable phosphors, and the mixing ratio of binders tostimulable phosphors. However, said thickness is preferably in the rangeof 10 to 1,000 μm, and is more preferably in the range of 10 to 500 μm.

The radiation image conversion panel according to the present inventionis described.

A phosphor sheet, prepared by applying the stimulable phosphor layeronto a support, is then cut into specified sizes.

Any of several common methods may be employed for cutting. However, fromthe viewpoint of workability as well as accuracy, trimming machines orpunching machines are preferred. The radiation image conversion panel ofthe present invention is preferably provided with a protective layer(hereinafter occasionally referred to as a protective film) in order tochemically and physically protect the surface of the stimulable phosphorlayer. Said protective layer may be suitably constituted based on itspurposes as well as its use.

Examples of protective layers to cover said stimulable phosphor layermay be polyester film, polymethacrylate film, nitrocellulose film, andcellulose acetate film, provided with a stimulating light absorbinglayer at a haze ratio of 5 to 60 percent, determined by the methoddescribed in ASTMD-1003. Of these, from the viewpoint of transparency aswell as strength, stretched films such as polyethylene terephthalatefilm and polyethylene naphthalate film are preferred, and from theaspect of moisture resistance, metallized films are specificallypreferred, which are obtained by applying a thin layer comprised ofmetal oxides or silicone nitride onto said polyethylene terephthalatefilm or polyethylene naphthalate film through vacuum evaporation.

The haze ratio to obtain the effects of the present invention ispreferably from 5 to 60 percent, and is more preferably from 10 to 50percent. A haze ratio of less than 5 percent is not preferred, sinceeffects to minimize image unevenness, as well as to minimize linearnoise, decrease. On the other hand, said haze ratio of more than orequal to 0.60 percent is also not preferred, since sharpness enhancingeffects are degraded.

In order to satisfy required moisture resistance, optimal moistureresistance is obtained by laminating a plurality of resinous films andmetallized films obtained by vacuum-evaporating metal oxides onto saidresinous film. In order to minimize degradation of stimulable phosphorsdue to moisture absorption, it is preferable to achieve no more than 50g/m²·day. The method of laminating a resinous film is not speciallylimited and known conventional methods can be applied.

Further, an excitation light absorbing layer is preferably providedbetween the laminated resinous films so that said excitation lightabsorbing layer is protected from physical impact as well as chemicalmodification so as to stabilize the plate functions over an extendedperiod of time. In addition, said excitation light absorbing layer maybe provided in a plurality of positions, and an adhesive layer forlamination may be comprised of coloring agents, thereby being utilizedas the excitation light absorbing layer.

A protective film may be provided a adhesion layer between a stimulablephosphor layer. However, a structure which covers all of the stimulablephosphor surface is preferred. This structure is called a “sealedstructure”. When a phosphor plate is sealed employing a protective film,it is possible to employ any of the several conventionally known methodssuch as a phosphor sheet which is interposed between moisture resistantprotective films and the peripheral edge of which is subjected tolamination under application of heat and pressure employing an impulsesealer, and lamination is carried out between rollers under applicationof heat and pressure. By employing a heat fusible resinous film as theresinous layer of the outermost layer in contact with the phosphor sheetof the moisture resistant protective film, the moisture resistantprotective film is fused, whereby the efficiency of sealing work of thephosphor sheets is enhanced. The moisture resistant protective film ispreferably provided on both sides of the phosphor sheet and theperipheral edge of said moisture resistant protective films, which islocated beyond the peripheral edge of said phosphor sheet, is fused toresult in a sealed structure, whereby it is possible to prevent infusionof water from the outside. Further, the moisture resistant protectivefilm on one side of the support may be laminated with at least onealuminum film. By employing such a support, it is possible to assureminimal water infusion.

Further, said heat fusion, which is carried out employing an impulsesealer, is preferably performed under reduced pressure to minimize thedisplacement of the phosphor sheet in the moisture resistant protectivefilm and to remove moisture from the atmosphere.

Still further, the phosphor surface may or may not be allowed to comeinto contact with the heat fusible resinous layer of the outermost layeron the side in contact with the phosphor surface of the moistureresistant protective film. The non-contact state, as described herein,refers to the state in which the phosphor surface and the moistureresistant protective film are optically and mechanically handled mostlyas discontinuous body, even though they may come into “point” contact.Further, the heat fusible film, as described herein, refers to theresinous films which are fusible in the generally used impulse sealer,and include, for example, ethylene-vinyl acetate copolymers (EVA),polypropylene (PP) film, and polyethylene (PE) film. However, thepresent invention is not limited to these examples.

EXAMPLES

The invention is described below referring examples.

Preparation of Phosphor Sheet

Preparation of Phosphor Sheet 1: Mixture Flame Spraying Method,Inventive Example

(Preparation of Phosphor A)

For synthesizing a phosphor precursor of a europium-activated bariumfluoroiodide, 2780 ml of an aqueous solution of BaI₂ (3.6 moles/liter)and 27 ml of an aqueous solution of EuI₃ (0.15 moles/liter) were putinto a reaction vessel and held at 83° C. while stirring. After that,322 ml of an aqueous solution of ammonium fluoride (8 moles/liter) wasadded through a roller pump into the reaction mother liquid to prepareprecipitation. The temperature keeping and the stirring were continuedfor 2 hours after the addition for ripening the precipitation.

The precipitation was filtered, washed by methanol and dried in vacuum,thus crystals of europium-activated barium fluoroiodide were obtained.For preventing the variation in the particle shape and the particle sizedistribution caused by sintering on the occasion of baking, 0.2% byweight of an extremely fine powder of alumina was added and sufficientlystirred by a mixer so as to uniformly adhere the alumina fine-particlesonto the crystal surface. The crystals were filled in a quartz boat andbaked for 2 hours at 850° C. in hydrogen atmosphere using a tube furnaceand crushed in a mortar and then classified to prepare Phosphor A havingan average particle diameter of 9 μm.

(Formation of Composite Layer)

A raw material powder to be flame sprayed was prepared by mixing 10% byweight of nylon powder having a melting point of 180° C. and a particlediameter of 30 to 200 μm as the thermoplastic resin and 90% by weight ofthe above prepared Phosphor. A as the inorganic particles. An aluminumplate having a thickness of 0.1 mm was employed as the substrate to besprayed; the plate was subjected to a blast treatment by blastingalumina grit (granule degree of #20) at a pressure of 0.5 MPa, and topreliminary heating treatment by heating by 170° C.

The raw material powder containing the phosphor was flame sprayed by thelow temperature flame spraying method on to the aluminum plate under thefollowing conditions.

(Spraying Condition)

-   -   Burning gas: Oxygen gas (pressure: 350 kPa), propane gas        (pressure: 350 kPa) and air (pressure: 560 kPa)    -   Flame temperature: 900° C.    -   Flame velocity: 150 m/second    -   Spraying distance: 350 mm    -   Supplying amount of raw material powder: 50 g/second

The above flame temperature was a temperature at which the nylon powderas the thermoplastic resin was melted or partially melted and thePhosphor A was not molted or not partially molted.

The thickness of the layer of thus obtained Phosphor Sheet 1 was 210 μm.

Preparation of Phosphor Sheet 2: Mixture Flame Spraying Method,Comparative Example)

Phosphor Sheet 2 was prepared in the same manner as in Phosphor Sheet 1except that the content of the nylon powder as the thermoplastic resinand that of the Phosphor A were each varied to 40% and 60% by weight,respectively, and the thickness of the layer was varied to 310 μm.

Preparation of Phosphor Sheet 3: Mixture Flame Spraying Method,Comparative Example

Phosphor Sheet 3 was prepared in the same manner as in Phosphor Sheet 1except that the spraying conditions were changed as follows.

-   -   (Flame spraying condition)    -   Burning gas: Oxygen gas (pressure: 1.2 MPa), hydrogen gas        (pressure: 1 MPa) and air (pressure: 700 kPa)    -   Flame temperature: 2700° C.    -   Flame velocity: 2100 m/second    -   Spraying distance: 225 mm    -   Supplying amount of raw material powder: 80 g/second

At the above temperature, both of the nylon powder as the thermoplasticresin and Phosphor A were melted or partially melted.

Preparation of Phosphor Sheet 4: Mixture Flame Spraying Method,Inventive Example

(Preparation of Phosphor B)

A europium-activated barium fluorobromide phosphor BaFBr: 0.001Eu²⁺ wasprepared according to the following procedure.

Into a reaction vessel, 1780 ml of an aqueous solution (4.5 moles/liter)of NH₄Br, 5 ml of an aqueous solution (0.2 moles/liter) of EuBr₃ and 215ml of water were charged. The reaction liquid in the reaction vesselhaving a concentration of NH₄Br 4.0 moles/liter was kept at 60° C., andthen 100 ml of an aqueous solution (10 moles/liter) of NH₄F and 400 mlof an aqueous solution (2.5 moles/liter) of BaBr₂ were separately addedto a mixing room in the reacting liquid using precise cylinder pumpswhile stirring and keeping the temperature so that the mole ratio ofNH₄F and BaBr₂ is held at constant.

Thus formed precipitation of precursor crystals were filtered and washedby 2 liter of methanol. The washed precursor crystals were putout anddried under vacuum for 4 hours at 120° C., thus 220 g ofeuropium-activated barium fluorobromide crystals were obtained. Forpreventing the variation of the particle shape and the particle sizedistribution caused by sintering on the occasion of baking, 0.2% byweight of an extremely fine powder of alumina was added and sufficientlystirred by a mixer so as to uniformly adhere the alumina fine particlesonto the crystal surface. One hundred grams of the crystals were filledin a quartz boat and baked for 2 hours at 850° C. in nitrogen atmosphereusing a tube furnace to prepare Phosphor B of europium-activated bariumfluorobromide (BaFBr:0.001Eu²⁺). The average particle diameter of thephosphor was 9 μm.

(Flame Spraying Conditions)

A phosphor layer was formed under the same flame spraying conditions asin Phosphor Sheet 1 except that the Phosphor B is employed in place ofthe Phosphor A to prepare Phosphor Sheet 4.

Preparation of Phosphor Sheet 5: Mixture Flame Spraying Method,Comparative Example

Phosphor Sheet 5 was prepared in the same manner as in Phosphor Sheet 4except that the flame spraying conditions were changed to thefollowings.

(Flame Spraying Condition)

-   -   Burning gas: Oxygen gas (pressure: 1.2 MPa), hydrogen gas        (pressure: 1 MPa) and air (pressure: 700 kPa)    -   Flame temperature: 2700° C.    -   Flame velocity: 2100 m/second    -   Spraying distance: 225 mm    -   Supplying amount of raw material powder: 80 g/second

At the above temperature, both of the nylon powder as the thermoplasticresin and Phosphor A were melted or partially melted.

Preparation of Phosphor Sheet 6: Flame Spraying Method Using CompositeParticles, Inventive Example

In 500 parts of methyl ethyl ketone dissolving therein 10 parts of BL-S(poly(vinyl butyral) manufactured by Sekisui Chemical Co., Ltd.), 90parts of Phosphor A used in the preparation of Phosphor Sheet 1 wasdispersed and granulated by drying by a spray dryer (FL-12, manufacturedby Ohkawara Kakohki Co., Ltd.) at a drying temperature of 100° C. innitrogen atmosphere for reducing the methyl ethyl ketone content in theproduct by less than 1% by weight to composite particles composed of thephosphor particles and the thermoplastic resin. The average diameter ofthe composite particles was 11 μm in volume-equivalent particlediameter.

(Flame Spraying Conditions)

Phosphor Sheet 6 was prepared in the same manner as in Phosphor Sheet 1except that nylon resin as the thermoplastic resin was not employed.

Preparation of Phosphor Sheet 7: Flame Spraying Method Using CompositeParticles, Comparative Example

Phosphor Sheet 7 was prepared in the same manner as in Phosphor Sheet 6except that the flame spraying conditions were changed to thefollowings.

(Flame Spraying Condition)

-   -   Burning gas: Oxygen gas (pressure: 1.2 MPa), hydrogen gas        (pressure: 1 MPa) and air (pressure: 700 kPa)    -   Flame temperature: 2700° C.    -   Flame velocity: 2100 m/second    -   Spraying distance: 225 mm    -   Supplying amount of raw material powder: 80 g/second

At the above temperature, both of the poly(vinyl butyral) resin as thethermoplastic resin and Phosphor A were melted or partially melted.

Preparation of Florescent Sheet 8: Mixture Flame Spraying Method,Inventive Example

(Preparation of Phosphor A2)

In a methanol dispersion containing the following compounds, 100 g ofPhosphor A used in the preparation of Phosphor Sheet 1 was immersed toprepare slurry. The slurry was filtered, crushed in a mortar and driedat 80° C. for 3 hours and classified to prepare Phosphor A2 having anaverage particle diameter of 10 μm. Phosphor Sheet 8 was prepared byforming a phosphor layer under the same conditions as in Phosphor Sheet1.

-   -   Silane coupling agent (γ-mercaptopropyltrimethoxysilane) 5.0 g    -   Hydrophilic fine particle (Silica Particle manufactured by Nihon        Aerosil Co., Ltd., average particle diameter: 12 nm) 0.5 g    -   Phosphor sheet 8 was prepared by forming a phosphor layer in the        same flame spraying conditions as in Phosphor Sheet 1.

Preparation Phosphor Sheet 9: Mixture Flame Spraying Method, ComparativeExample

Phosphor Sheet 9 was prepared in the same manner as in Phosphor Sheet 8except that the flame spraying conditions were changed as follows.

(Flame Spraying Condition)

-   -   Burning gas: Oxygen gas (pressure: 1.2 MPa), hydrogen gas        (pressure: 1 MPa) and air (pressure: 700 kPa)    -   Flame temperature: 2700° C.    -   Flame velocity: 2100 m/second    -   Spraying distance: 225 mm    -   Supplying amount of raw material powder: 80 g/second

At the above temperature, both of the nylon powder as the thermoplasticresin and Phosphor A2 were melted or partially melted.

(Observation of the Surface of the Phosphor Sheet)

The surface of each of the above-prepared phosphor sheets was visuallyobserved to examine the color thereof. Results of the observation arelisted in Table 1.

Preparation of Moisture-Proof Protective Film

A protective film having the following constitution A to be providedonto the phosphor layer side of each of the above-prepared phosphorsheets was prepared.

Constitution A

-   -   NY15///VMPET12///VMPET12///PET12///CPP20    -   NY: Nylon    -   PET: Poly(ethylene terephthalate)    -   CPP: Casting polypropylene        MVPET: Alumina-deposited PET (manufactured by Toyo Metalizing        Co., Ltd., available on the market)

The number after each of the resin film is the thickness in μm of therein layer and “///” represents a dry lamination adhesive layer having athickness of 3.0 μm. The adhesive used for the dry lamination was atwo-liquid reactive type urethane adhesive.

A dry laminated film composed of CCP 30 μm/Aluminum film 9μm/Poly(ethylene terephthalate) 188 μm was prepared for a protectivefilm to be provided on the back side of the aluminum plate as thesubstrate of the phosphor sheet. The thickness of the adhesive layer was1.5 μm and a two-liquid reactive type urethane adhesive was used.

Preparation of Radiation Image Conversion Panel

Radiation Image Conversion Panels 1 through 9 were prepared by cuttingeach of the phosphor sheets into a shape of 20 cm square and piled withthe above-prepared protective films, and then the edges of the filmswere sealed by an impulse sealer under reduced pressure. The distancebetween the edge of the phosphor sheet and the sealed portion was 1 mm.The width of the heater of the impulse sealer was 3 mm.

Evaluation of the Radiation Image Conversion Panel

The luminance and the sharpness of the above-prepared radiation imageconversion panels were evaluated according to the following procedure.

(Measurement of Luminance)

Each of the radiation image conversion panels was irradiated by X-raysgenerated by applying a valve voltage of 80 kV and stimulated by He—Nelaser light (633 nm). The intensity of the stimulation light emittedfrom the phosphor layer was measured by a light receiving device (aphotomultiplier having spectral luminance S-5) and defined as theluminance. The luminance was represented by relative value when theluminance of Radiation Image Conversion Panel was defined as 100.

(Measurement of Sharpness)

Each of the phosphor panels was irradiated by X-rays generated byapplying a valve voltage of 80 kV through a lead MFT chart, and then thepanel was stimulated by the He—Ne laser light. The emitted light wasreceived by the above-mentioned light receiving device for converting toelectric signals. The electric signals was subjected to analogue/digitalconversion and recorded on a hard disc. The recorded signals wereanalyzed by a computer to examine the modulation transfer function (MFT)of the X-ray image recorded on the hard disc. The MFT value (%) at aspace frequency of 1 cycle/mm was determined. Higher MFT value ispreferred since a shaper image can be obtained. It is necessary that thesharpness exceeds 65% for practical use as the radiation imageconversion panel.

Results obtained by the above tests are listed in Table 1. TABLE 1Radiation Evaluation image Phosphor Relative conversion Phosphorpreparation lumines- Sharpness panel No. sheet No. method Surface cence(%) 1 1 Mixture White 102 68 flame spraying 2 2 Mixture White 100 60flame spraying 3 3 Mixture Brown 95 62 flame spraying 4 4 Mixture White101 69 flame spraying 5 5 Mixture Brown 90 54 flame spraying 6 6 MixtureWhite 103 68 flame spraying 7 7 Mixture Brown 94 59 flame spraying 8 8Mixture White 102 69 flame spraying 9 9 Mixture Brown 95 61 flamespraying

As is cleared by the results in Table 1, the radiation image conversionpanel according to the invention having the phosphor layer formed byflame spraying under the condition, in which the temperature iscontrolled so that the thermoplastic resin is melted or partially moltedand the inorganic particles are not melted or not partially melted andthe contents of the inorganic particles and the thermoplastic resin arewithin the condition defined in the invention, is not irregularlycolored in the phosphor layer, emits high luminescent light and isexcellent in the sharpness compared with the comparative examples.

1. A method for forming a composite layer comprising inorganic particlesand a thermoplastic resin, which comprises a step of flame spraying amixture of the inorganic particles and the thermoplastic resin to asubstrate at a temperature of not less than the glass transition pointof the thermoplastic resin and not more than melting point of theinorganic particles, wherein the mixture comprises 85-99% by weight ofthe inorganic particles and 15-1% by weight of the thermoplastic resin,total weight of the mixture being 100% by weight.
 2. The method of claim1, wherein the thermoplastic resin in the mixture is thermoplastic resinparticles.
 3. The method of claim 1, wherein the inorganic particles arephosphor.
 4. The method of claim 1, wherein the mixture is a compositeparticles comprising the inorganic particles and the thermoplasticresin.
 5. The method of claim 4, wherein the composite particles arecore shell particles.
 6. The method of claim 5, wherein each of the coreshell particles has an inorganic particle core and a thermoplastic resinshell.
 7. The method of claim 1, which further comprises a step, priorto flame spraying, of subjecting surface of the inorganic particles totreating with a silane coupling agent.
 8. The method of claim 4, whereinthe mixture is prepared by a method comprising treating surface of theinorganic particles with a silane coupling agent, and the surfacetreated inorganic particles are mixed with the thermoplastic resin. 9.The method of claim 8, wherein the surface treated inorganic particlesare mixed with the thermoplastic resin particles.
 10. The method ofclaim 1, wherein the mixture of the inorganic particles and athermoplastic resin is composite particles each of which comprises theinorganic particles and a thermoplastic resin.
 11. The method of claim10, wherein the composite particles are core shell particles comprisingthe inorganic particles and a thermoplastic resin.
 12. The method ofclaim 11, wherein the core shell particles are prepared by a methodcomprising treating surface of the inorganic particles with a silanecoupling agent, and the surface treated inorganic particles are mixedwith the thermoplastic resin.
 13. The method for forming a compositelayer comprising inorganic particles and a thermoplastic resin, whichcomprises a step of flame spraying composite particles each whichcomprises the inorganic particles and the thermoplastic resin to asubstrate.
 14. The method of claim 13, wherein the inorganic particlesare phosphor.
 15. A composite layer prepared by a method of claim
 1. 16.A radiation image conversion panel prepared by employing the compositelayer prepared by a method of claim 3.